<template>
  <div>
    <router-link
      tag="div"
      class="header-abs"
      to="/"
      v-show="showAbs"
    >
      <span class="iconfont">&#xe624;</span>
    </router-link>
    <div
      class="header-fixed"
      v-show="!showAbs"
      :style="opacityStyle"
    >
      项目详情
      <router-link to="/">
        <span class="iconfont">&#xe624;</span>
      </router-link>
    </div>
  </div>
</template>

<script>
export default {
  name: 'DetailHeader',
  data () {
    return {
      showAbs: true,
      opacityStyle: {
        opacity: 0
      }
    }
  },
  methods: {
    handleScroll () {
      const top = document.documentElement.scrollTop
      if (top > 60) {
        let opacity = top / 140
        opacity = opacity > 1 ? 1 : opacity
        this.opacityStyle = { opacity }
        this.showAbs = false
      } else {
        this.showAbs = true
      }
    }
  },
  activated () {
    window.addEventListener('scroll', this.handleScroll)
  },
  deactivated () {
    window.removeEventListener('scroll', this.handleScroll)
  }
}
</script>

<style lang="stylus" scoped>
@import('~styles/varibles.styl')
.header-abs{
  width .8rem
  height .8rem
  line-height .8rem
  text-align center
  background #000
  opacity .4
  border-radius .8rem
  color #fff
  position absolute
  left .2rem
  top .2rem
}
.header-fixed {
  height $headerHeight
  line-height $headerHeight
  background $bgColor
  color #fff
  text-align center
  font-size .32rem
  position fixed
  left 0
  top 0
  right 0
  bottom 0
  span{
    color #fff
    position absolute
    left .2rem
    top 0
    font-size: .35rem
  }
}
</style>
